1. Field of the Invention
The present invention relates, in general, to a method for rapid robotic handling of small articles removed from molds. More specifically, the present invention pertains to such a method which is particularly well suited for removing the articles from a molding machine having molds in which they are molded, and thereafter carrying the articles within a very short period of time away from the molds and depositing the articles for further processing in a high speed, automated production system.
2. Description of the Prior Art
Recently, attention has been directed by industry toward economically forming large quantities of high-quality contact lenses in a precisely operating, high-speed automated molding system. In such a lens molding system, each lens is formed by sandwiching a monomer in an interspace which is present between front and back mold sections, normally identified as, respectively, front and base or back curves. The monomer is polymerized to form a contact lens, which is then removed from the mold sections, further treated and then packaged for consumer use.
The mold sections used in the above-mentioned process may themselves be formed through the intermediary of injection molding or compression molding processes. These mold sections may be made the family of materials consisting of thermoplastics; for example, preferably such as polystyrene, which has been determined to constitute an excellent material for making these mold sections. Polystyrene does not chemically react with the hydrophilic material normally employed to make the contact lenses; for instance, such as hydroxy ethylene methacrylate (HEMA). Therefore, it is possible to form very high quality contact lenses of that type of material in polystyrene molds. In addition, polystyrene is widely available in industry and commerce and, as a result, is relatively inexpensive. Because of the ease and low cost with which polystyrene mold sections may be produced and then employed to mold contact lenses, each pair of complementary front and base curve polystyrene mold sections is typically used only a single time in order to mold only one contact lens, and may then be discarded or recycled for other uses.
In the above-discussed automated contact lens production system, it is desirable to eliminate or to minimize any exposure to oxygen of the hydrophilic monomer used for the manufacture of the contact lenses. Correspondingly, it is desirable to eliminate or minimize the exposure of the lens mold sections to oxygen. Therefore, when the polystyrene mold sections are formed and then used for the purpose of making contact lenses in the above-discussed manner, it is desirable to rapidly transfer these mold sections from the mold in which they are made to a low oxygen (preferably nitrogen) environment. It has been difficult to achieve the desired transfer speed with conventional robot assemblies or controls because presently available robots do not move with adequate rapidity and precisely enough to enter into, and exit from, the molding apparatus at the desired rate of speed in effectuating the removal of the molded articles. In particular, if these robots are operated at the necessary rate of speed, they tend to waffle and shake or vibrate undesirably as they come to a sudden stop, and the movements of the robot are resultingly not sufficiently precise. On the other hand, if the robots are slowed down so as to be able to move more precisely, the robots no longer possess the desired speed to facilitate the contact lens mass-producing process.
Moreover, in the above-mentioned automated contact lens production system, the contact lens mold sections may not be fully solidified when they are ejected or removed from the mold in which they are formed. It is, therefore, important that any robot or apparatus which is used to carry the contact lens-forming mold sections away from that mold will not interfere so as to adversely affect the desired optical qualities of the contact lens mold sections. In particular, it is important that any such robot or apparatus be capable of absorbing the kinetic energy of the lens mold sections as they are being transferred to such transporting robot or apparatus without deleteriously altering the shape, form or dimensions of the lens mold sections. The robot and mold transfer method employed must, likewise, be able to transport the lens mold sections in a manner that permits those lens mold sections to cool and completely harden in a desired manner.
In addition, in order to maximize the optical quality of the contact lenses, it is preferred that the optical surfaces of the front and base curve polystyrene mold sections; that is, the surfaces of those mold sections which touch or lie against the hydrophilic monomer as the lens preform is being molded, not be engaged or contacted by any mechanical handling equipment while the mold sections are being transported by and positioned in the lens molding system.
In order to achieve the foregoing kind of transport system, pursuant to the disclosure of copending U.S. patent application Ser. No. 08/258,267, continued as U.S. patent application Ser. No. 08/757,154, now issued as U.S. Pat. No. 5,681,138, there is described an apparatus for removing and transporting ophthalmic or contact lens mold sections from a mold, and which generally comprises first, second and third assemblies. The first assembly removes the lens mold sections from the mold and transports the lens mold sections to a first location, the second assembly receives the lens mold sections from the first assembly and transports the lens mold sections to a second location, and the third assembly receives the lens mold sections from the second assembly and transports the lens mold sections to a third location. Preferably, the first assembly comprises a hand including vacuum structure to receive the lens mold sections from the mold and to releasably hold the lens mold sections, and a support subassembly connected to the hand to support the hand and to move the hand between the mold and the first location.
The second assembly preferably includes a support frame, a platform to receive the lens mold sections from the first assembly and supported by the support frame for movement between the first and second locations, and moving means for moving the platform along the support frame and between these first and second locations.
The preferred design of the third assembly includes a transport subassembly and a support column. The transport subassembly receives the lens mold sections from the second assembly, releasably holds those lens mold sections, and carries the lens mold sections to the third location; and the support column supports the transport subassembly for movement between the second and third locations.
In an effort designed to simplify and provide further improvements on the foregoing transport apparatus, alternative embodiments have been developed more recently, as disclosed in copending U.S. patent application Ser. No. 08/431,884, continued as U.S. patent application Ser. No. 09/048,859, now issued as U.S. Pat. No. 5,980,184, which discloses an apparatus for removing and transporting articles, such as ophthalmic contact lens mold sections, or primary contact lens packaging elements, such as the base members of blister packages, from a mold. The apparatus, in one embodiment thereof, which is employed in the manufacture of lens mold base curves, includes first, second, and third assemblies; the first of which removes the articles from the molding station at a first location and transports them to a second location; the second assembly receives the articles from the first assembly and transports them to a third location, and the third assembly receives the articles from the second assembly and transports them to a fourth location.
A second embodiment of the apparatus which is used in the forming of lens mold front curves additionally includes a flipper assembly disposed between the first and third assemblies, which flipper assembly receives the articles from the first assembly and inverts them before depositing them onto the third assembly. This second embodiment is useful in conjunction with molded articles which are transported to the flipper assembly in an inverted position.
A third embodiment, which produces primary packaging components, such as the base members of blister packages for housing the contact lenses, includes second and third assemblies which further include means for altering the relative spacing between the articles while the articles are being transported.
Although the foregoing embodiments and operative versions of the apparatus, as elucidated in the aforementioned copending U.S. patent applications, are employable in providing the molded components constituting mold sections for forming contact lenses, and also primary package elements for contact lenses, such as the contact lens-receiving base members of blister packages, there are problems associated with vibration, speed and rejection of molded components overly exposed to oxygen. The numerous operating and transfer assemblies and stations which are required for transporting the molded components at high rates of speed from the molding installation in which they are formed to their ultimate depositions onto pallets for further treatment, such as in a low oxygen or nitrogen atmosphere, are of considerable complexity, subject to waffling and vibration and rendering the efficacy of producing acceptable articles difficult to maintain as a result of the multiplicity of operative apparatus components, and transfer and transport paths employed in the various apparatus embodiments. For example, numerous programmable logic controllers (PLCs) used to individually control various sections of the assemblies and stations prevent increasing operating speeds and reducing oxygen exposure time. This is due, for example, to the time needed for the PLCs to communicate with each other or with other PLCs of downstream or upstream assemblies.
Pursuant to the present invention, there is contemplated a simplified method that increases speed of operation of assemblies for transferring and transporting high quality articles which have been molded, such as contact lens mold sections and primary package elements for contact lenses. This is achieved by replacing various programmable logic controllers (PLCs) by a supervisory microprocessor that increases communication and synchronization between the molding apparatus and an ultimate conveyance element, such as a pallet, for transporting these molded articles into a nitrogen or low oxygen environment or other desired location for further processing.
The object of the present invention is to provide a computer controlled method for removing and transporting ophthalmic lens fabricating mold sections from a molding device to an inert chamber in a predetermined time that eliminates the problems of conventional methods.
Another object of the present invention is to provide a method that eliminates various programmable logic controllers (PLCs).
Yet another object of the present invention is to provide a method that reduces response time in processing molded components, and quickly determining and discarding unacceptable molded components without disrupting the continuous operation of assemblies, including upstream and downstream assemblies.
A further object of the present invention is to provide a method that includes rapid communication with upstream and downstream assemblies, and precise high speed, as well as vibration and shock free, movement to transfer among the various assemblies molded articles, which may not yet be completely cured or hardened, without causing undue plastic deformations of the articles.
A still further object of the present invention is to provide a method that includes multi-tasking, where various tasks are controlled by a supervisory microprocessor.
An additional object of the present invention is to provide a method that accurately determines total oxygen exposure time to correctly reject overly exposed mold components, and rapidly remove and transport articles made from the family of thermoplastics, such as polystyrene, from a mold in which those articles are made through the intermediary of sophisticated robotics, into a low oxygen environment of an automated contact lens molding system, within a period or time interval of only a few seconds.
A still further object of the present invention is to provide a method that removes a plurality of discrete molded articles from a mold with the molded articles arranged in a matrix array, and to selectively either preserve that matrix array during subsequent handling of the molded articles, or reorient the matrix and the relative spacing of the molded articles therein according to a second predetermined matrix prior to being transported to a further locale.
These and other objects of the inventions are achieved by a method by a central processor controlled for removing and transporting ophthalmic lens fabricating mold sections from a molding device to an inert chamber in a predetermined time comprising the steps of:
starting a timer upon opening the molding device and exposing the mold sections;
actuating a robotic arm to transport the mold sections from the molding device to an intermediate position;
actuating a cam-controlled arm to transport the mold sections from the intermediate position to a pallet held on a conveyor belt at a cam-arm pre-part release location; and
releasing the pallet to move on the conveyor belt to the inert chamber.
A further step includes identifying molded articles as unacceptable when the pallet enters the inert chamber in a time that exceeds the predetermined time.
The robotic arm actuating step includes the steps of:
accelerating the robotic arm along a curvilinear path from a waiting position to an opening in the molding device in a synchronism with the opening of the molding device, in accordance with acceleration parameters stored in a memory of a central processor; and
decelerating the robotic arm after an acceleration time stored in the memory, where the robotic arm is approximately in the opening of the molding device, to provide a damping effect for allowing transfer of the mold sections from the molding machine to the robotic arm.
A further embodiment includes the steps of:
generating control parameters for a plurality of motors to effectuate a curvilinear motion of the robotic arm between the waiting position and the opening of the molding device;
storing the control parameters in the memory of the central processor;
opening the molding device and exposing the mold sections;
accelerating the robotic arm along a curvilinear path from the waiting position to the opening in the molding device in a synchronism with the opening of the molding device, in accordance with the control parameters stored in the memory; and
decelerating the robotic arm when the robotic arm is approximately in the opening of the molding device, to provide a damping effect for allowing transfer of the mold sections from the molding machine to the robotic arm.
Illustratively, the control parameters for each of the motors include acceleration and deceleration parameters, and acceleration and deceleration time parameters.
Additional steps includes raising a nest to receive the mold sections at the intermediate position; lowering the nest after transfer thereon of the molded sections from the robotic arm; and transferring the molded sections from the lowered nest to the cam-controlled arm. A further step includes, in the case the mold sections are primary package molds for example, actuating cylinders to rotate and resize the mold sections.
The cam-controlled arm movement includes moving the cam-controlled arm to the intermediate position; lowering the cam-controlled arm to pick the molded sections from a nest that receives the mold sections from the robotic arm; raising the cam-controlled arm up to the intermediate position after picking the molded sections from the nest; moving the cam-controlled arm to the pallet; lowering the cam-controlled arm while raising the pallet from the cam-arm pre-part release location to a cam-arm part release location; and transferring the molded sections from the cam-controlled arm to the pallet.
Alternatively, the cam-controlled arm movement includes moving the cam-controlled arm to a first position aligned with the intermediate position at a center height of the cam-controlled arm which is lower than the intermediate position; raising the cam-controlled arm to the intermediate position from first position to pick the molded sections from the robotic arm; moving the cam-controlled arm down from the intermediate position to the first position after picking the molded sections; relocating the cam-controlled arm along the center height to a second position aligned with the cam-arm pre-part release location; lowering the cam-controlled arm to the cam-arm part release location; raising a pallet from the cam-arm pre-part release location to the cam-arm part release location; and transferring the molded sections onto the pallet. Illustratively, the relocating step further includes rotating the cam-controlled arm by approximately 180xc2x0 around an axis longitudinal thereto.
Initializing the robotic and cam-controlled arms are performed, as needed, to position them collision free zones.
With respect to the pallet that receives the molded articles for transport to the inert chamber on the conveyor belt, the following steps are performed:
raising the pallet from the cam-arm pre-part release location to the cam-arm part release location;
transferring the molded sections from the cam-controlled arm to the pallet; and
lowering the pallet containing the molded section from the cam-arm part release location to the cam-arm pre-part release location.
Prior to the pallet releasing step, the following steps may be performed: actuating a pallet stop device to stop the pallet at the cam-arm pre-part release location; actuating a lift to raise the pallet held at the cam-arm pre-part release location by the pallet stop device in order for the pallet to receive the molded articles from the cam-controlled arm; and actuating a pallet locate device to hold the raised pallet at the cam-arm release location.
Pallets may be held in a que upstream from the pallet that receives the molded articles from the cam-controlled arm located at the cam-arm pre-part release location; and released one at a time to proceed to the cam-arm pre-part release location. Releasing these pallets in the que includes actuating a cylinder that simultaneously releases a first pallet in the que and holds a second pallet.
Alternatively two cylinders are used to release the pallets in the que one at a time. In this case, the following steps are performed: actuating a first cylinder which holds the first pallet located in the que; and actuating a second cylinder which releases the second pallet located downstream from the first pallet.
In a racetrack mode, actuating the robotic arm transports the mold sections from the molding device to a discard bin for discarding the molded articles, while empty pallets move on the conveyor belt to the inert chamber. Similarly, in a sample mode, actuating the robotic arm transports the mold sections from the molding device to a sample pallet located at the discard bin location, where the sample pallet is moved from a standby position to the discard location for receiving the mold sections from the robotic arm.
In another embodiment, whether a first pallet is located in a que position of the conveyor belt is determined. When the first pallet is located in the que position, then the robotic and cam-controlled arms are actuated.